Brix, ph, acid, and sulfite

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1 Brix, ph, acid, and sulfite by John Merkle, Sept. 18, 2014 Basics of chemical control for winemaking

2 Brix Sugar dissolved in water; 1ºBrix=1% sugar Grape juice is mostly sugar in water Hydrometer in cylinder measures Brix via scaled floating tube See chart for Brix scale and sugar content

3 SG Gravity Brix Sugar (lb&oz/us gal.) PA (%) degrees degrees ((SG-1) 220)+1.6 lb oz 0.6Br

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5 Refractometer Can use refractometer before fermentation begins, but not after

6 Adjusting Brix If Brix, no adjustment needed, depending on wine type If too high, dilute with water If too low, add sugar in water (simple syrup) 10 g/l (1.33oz/gal) of sugar will raise Brix 1º

7 ph - measure of acidity ph is the negative logarithm of the Hydrogen ion concentration ph tests for acidity versus alkalinity ph 3.0 has 10 times the acid as ph 4.0

8 ph meters and buffers

9 ph meter should read to 2 decimal places, and have accuracy of.01 ph units Use 2 buffers for accurate calibration Start with ph 7 buffer and end with ph 4 buffer Rinse well between buffers and samples using distilled or deionized water ph meters

10 ph critical control ph of over or so can cause many problems: flat tasting wine, microbial growth, poor aging Must/juice ph before fermentation should be 3.5 or lower; adjust with tartaric acid for grape wines Sulfite adds are greatly reduced at lower ph

11 ph critical control ph less than 3.6 before cold stabilization ph in finished wine 3.3 to 3.6 normally ph affects color of wine (low ph is more reddish, high ph is more towards purple)

12 Acidity - importance Titratable acidity (TA, total acid) Tartaric is dominant in concentration, with malic and lactic in juice in lower amounts Fruit wines have more malic and citric acid Typical range in must is.6 to.9 TA, and in wine.5 to.75 % Acidity too high (strong) causes sourness, fermentation issues, and off-balance taste

13 Acidity testing for TA 5 ml sample to beaker (pipet for accuracy) If fermenting or MLF, microwave sample for 15 seconds before to drive off CO2 In red wine, titrate with 0.1 N sodium hydroxide (NaOH) solution by drops, to a green/blue end point; check with meter to ph 8.2 Multiply ml of sodium hydroxide solution used times 0.15 to get the TA %

14 TA endpoint in whites Same as red wine, but use phenolphthalein indicator, and titrate with.1 N sodium hydroxide (NaOH) to light pink endpoint (and/or check with meter to ph 8.2) Multiply ml NaOH x.15 = TA

15 Adjusting acid Adjust with tartaric acid in grape must/juice Add approx. 3.8 grams/gallon to raise TA by 0.1% (about 3/4 teaspoon) Always add half the amount calculated, as each must/juice/wine is buffered differently Lower TA if too high (above.9) with potassium (bi) carbonate (approx. 1g/L or 3.8 grams/gallon lowers TA by.1%)

16 Sulfite Management Sulfite, SO2, bisulfite, meta-bisulfite,... Protecting against oxygen and microorganisms Sulfite added to must/wine binds with chemicals and solids, reducing the concentration Amount needed is ph dependent Added at crush, throughout winemaking process, and before bottling

17 Ppm sulfite at ph levels

18 Sulfite Potassium meta-bisulfite (K-meta) most common Free sulfite, not total sulfite, is what matters Keep sulfite high enough (20-30 ppm free sulfite at low ph) If going with MLF later, keep sulfite level low Used throughout winemaking process (with citric acid) as sanitation control Better to have some in wine to be safe! Can test with Titrets, or kits (more accurate now)

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20 Sulfite testing (Ripper method) Simple with whites, not so easy with reds Pipet 20 ml (or use graduated cylinder) to flask Add 3 ml of starch indicator Add 5 ml of 25% sulfuric acid Quickly titrate with N Iodine Solution to blue color that holds for 30 seconds Multiply ml Iodine used x 40 to equal free sulfite level ((ml Iodine x N Iodine x 32000)/ml of wine sample)) Need to standardize Iodine solution frequently

21 Adjusting Sulfite Levels Campden tablets one source use 1 tablet per gallon of juice (30 ppm) Potassium meta-bisulfite most common dissolve in little water first before adding Free sulfite normally 50 to 80 ppm Add some (50 ppm) when crushing grapes Too much can cause some people to react adversely, or make the wine smell/taste bad

22 Making sulfite adds ppm (parts per million) equals mg/l (ppm free SO2/100 x x # gallons wine)/.57 = amount of bisulfite to add Example: For 5 gallons wine and ph 3.5, (want 40 ppm), and analyzed at 22 ppm. So, = 18 ppm bisulfite needed Then, (18/1000 x x 5)/.57 = 0.6 grams sulfite ( Equal to 6 ml of 10% stock solution of K-meta )

23 Analytical lab hands on Brix ph - calibration and measurement TA titration and calculation Sulfite analysis and calculation Recommended references: Home Winemaking-Jon Iverson (excellent for beginner) Techniques in Home Winemaking-Daniel Pambianchi (wine bible) MoreWinemaking.com has excellent reference guide (for reds)

24 Cheers to good winemaking